PROJECT 3 (Rollins) PROJECT SUMMARY Aging is the primary risk factor for numerous prevalent chronic conditions and diseases, including cancer, neurodegeneration, and cardiovascular disease. It is estimated that age-associated diseases cost the U.S. >$302 billion a year in healthcare expenditures. Slowing the rate of aging would increase the healthy years of life and simultaneously prevent or delay age-associated diseases. The last forty years has seen a revolution in our understanding of the biology of aging and the realization that aging can be manipulated genetically and environmentally. It has been well established in multiple invertebrate and vertebrate animal models that exposure to mild stressors such as caloric restriction (CR) protects against age-related diseases and increases healthy longevity. CR is known to activate the expression of pro-longevity genetic pathways. However, the mechanisms by which CR modulates pro- longevity gene expression are incompletely understood. Our recent studies in the genetic model organism C. elegans demonstrated for the first time that CR modulates the translation of various pro-longevity genes without affecting their transcription. Protein translation is mediated by the ribosome, a molecular machine comprised of up to 79 ribosomal proteins. While once considered static, the protein composition of the ribosome can vary. These compositional changes in turn can alter how specific mRNAs are selected for translation. We have shown recently that CR regulates the expression of ribosomal proteins in C. elegans. Knockdown in well-fed C. elegans of ribosomal proteins that are downregulated during CR mimics the effects of CR on longevity. Transcriptomic and proteomic data in humans, mice, fruit fly, yeast, and C. elegans have demonstrated that expression of ribosomal proteins is selectively altered with age. Taken together, these data suggest that regulated changes in ribosome composition may mediate the effects of CR on the translation of pro-longevity genes and the associated increase in lifespan. The overarching goal of this proposal is to begin defining how ribosome protein composition modulates mRNA translation and associated changes in health and longevity. Studies outlined in this proposal will test the hypothesis that changes in ribosomal protein composition associated with CR regulate longevity by modulating the translation of specific mRNAs. Our studies will also test the hypothesis that CR prevents age-related changes in ribosome protein composition and that this promotes the selective translation of pro-longevity genes. Detailed understanding of the molecular mechanisms by which CR modulates longevity is critical to understanding the aging process and for developing therapies that slow the onset and progression of age-related diseases in humans.